Powder inhaler with frusto-conical metering surface having dose indentations

ABSTRACT

The inhaler includes a storage chamber for the powder to be delivered and an inhalation passage through which air is drawn via a mouth piece. A metering member having a frustoconical side wall presents each dose to the inhalation passage in an upwardly open metering cup to be drawn therefrom by the air flow through the passage. A wiping element removes any particles of powder from the dispensing cup as it travels from the inhalation passage to the storage chamber to be refilled, and a chamber containing a moisture-absorbent material dries the empty cup and also dries the powder in the cup prior to inhalation to aid its removal from the cup. A mechanical counter is indexed each time the metering member is indexed to display the number of doses used or remaining.

This is a divisional application of Ser. No. 08/024,721, filed Jan. 6,1993 now U.S. Pat. No. 5,437,270.

TECHNICAL FIELD OF THE INVENTION

This invention relates to an inhaler, namely a device for use indelivering a dose of medicament or other substance for inhaling into thelungs.

BACKGROUND

The most common form of inhaler propels the dose of medicament inpressurised gas from an aerosol. However, this form of inhaler isbecoming less popular because of environmental and other considerations.The delivery of some drugs in a dry, finely divided form has been shownto have certain medical advantages over other forms of delivery.

Some known proposals for delivering medicament in a finely divided formcannot be operated by one hand. It is considered that one-handedoperation should be an important feature of such an inhaler.

EP 079478, EP 166294 and GB 2165159 all disclose dry powder inhalerswhich can be operated by one hand. In each of these proposals theinhaler includes a medicament storage chamber and an inhalation passagethrough which air is drawn via a mouthpiece. A metering member providedwith a metering recess transfers a dose of medicament from the storagechamber and deposits it in the inhalation chamber. It is considered thatthe accuracy of such an arrangement can be very poor: on the one hand,by repeated indexing of the metering member it is possible to deposittwo or more doses of medicament into the inhalation passage resulting inthe administration of an overdose of medicament; on the other hand,since the medicament normally drops from the metering recess into theinhalation passage under gravity, particles of medicament can adhere tothe interior of the metering recess so that an underdose is delivered.

U.S. Pat. No. 2,587,215 also discloses dry powder inhalers with the samedisadvantages as those mentioned above. However, this document alsodiscloses an embodiment in which the metering member presents themedicament in an upwardly open dispensing cup to a mixing chamber whereit is mixed with air before being sucked into an inhalation tube via anozzle having a narrow opening. Air sucked into the inhaler passes intothe inhalation tube either directly or through the mixing chamber andnozzle. Accordingly, not all the air passes over the dispensing cup. Ifmedicament adheres to the surface of the dispensing cup but is notsucked therefrom, there will be an underdose of medicament delivered tothe user. It is considered that, upon repeated use of the hollows todeliver doses to the inhalation passage, a continually increasing amountof the powder will adhere to the base of the hollow, resulting inprogressively decreased dosage to the patient. The tendency for abuild-up of adherent powder to occur is thought to be a source ofinaccurate dosing in many of the inhalers previously proposed. Themetering member is a rotary sliding device journalled on a cylindricalpivot member extending from the bottom of the body of the device. Suchan arrangement is susceptible to jamming due to ingress of powderbetween the cylindrical contacting surfaces of the pivot member and themetering member.

Another form of inhaler which is currently available includes a meteringmember including a number of tapered metering recesses which are open attop and bottom. In use, finely divided medicament from a storage chamberis packed into the recesses whereupon the metering member is moved to adispensing position in which air can be drawn through the recesses todraw out the medicament. This device is considered to have a number ofmajor shortcomings. Firstly, the metering recesses are prone toclogging. Secondly, a large amount of suction is required so that thedevice is unsuitable for many patients with breathing problems. Thirdly,two hands are required to operate the device.

The aim of the present invention may be viewed as being to provide aform of inhaler for one-handed operation which is capable ofadministering accurate doses and avoids the risk of multiple dosing. Afurther aim is to provide an inhaler which does not require a largeamount of suction for effective operation.

SUMMARY OF THE INVENTION

The present invention provides an inhaler for delivering a substance ina finely divided form, comprising a body defining a storage chamber forthe substance to be delivered and further defining an inhalation passagethrough which air is drawn via a mouthpiece; a metering member operableto transfer a volumetric dose of the substance from the storage chamberto the inhalation passage, the metering member having a metering surfacewhich is indented to provide at least one dispensing cup and beingmoveable between a first position in which a dispensing cup is presentedto the storage chamber to receive a dose of the substance and a secondposition in which a dose of the substance is presented to the inhalationpassage in a dispensing cup which is upwardly open in use; and cupclearing means for ensuring that the or each dispensing cup issubstantially free from the substance before being presented to thestorage chamber, the cup clearing means comprising means for moving theor each dispensing cup into a position from which, in normal use of theinhaler, any of the substance remaining in the dispensing cup would tendto fall, under the influence of gravity, out of the cup, after a dose ofthe substance has been presented in the cup to the inhalation passageand before that cup is again presented to the storage chamber.

Thus, in normal use of the inhaler repeated indexing of the meteringmember will not deposit multiple doses of the substance into theinhalation passage. Furthermore, removal of the substance from themetering member by the inhaled air flow rather than under gravity canensure that the dose is more thoroughly removed.

The cup clearing means may comprise an inhalation passage so formed thatthe dose of the substance presented to the inhalation passage issubjected to substantially the entire airflow through the inhalationpassage when air is drawn through the mouthpiece. Accordingly, whetherair is drawn into the inhaler through a single opening or throughseveral openings, the airflow through the device is such that all theair flows along a single duct at the point where the dispensing cup ispresented to the airflow within this duct.

The cup clearing means may additionally consist of or comprise resilientwiping means for dislodging any residual substance from the or each cupafter a dose of the substance has been presented therein to theinhalation passage and before that cup is again presented to the storagechamber. The provision of such dislodging means ensures that the or eachdispensing cup is cleaned prior to refilling, and thereby prevents abuild-up of adherent material with repeated refills.

Preferably, the metering member is resiliently biased into contact witha seat and is moveable while in contact with the seat. More preferably,the metering member is rotatable while in contact with the seat.

The metering member may comprise a frusto-conical side wall containingthe dispensing cup or cups. Such a side wall can include a plurality ofspaced-apart dispensing cups. The use of the frusto-conical shape in thewall of the metering member containing the dispensing cups allows a goodseal to be obtained between the metering member and a seat against whichthe frusto-conical wall mates. Accordingly, either rigid or semi-rigidplastics materials can be used, and the appropriate shapes can bemanufactured with relatively undemanding tolerances. Other shapes, suchas spherical or cylindrical shapes, either demand much tightertolerances in order to achieve the sort of seal required or resilientmaterials would have to be used or, possibly, an additional resilientsealing ring would have to be incorporated. The good seal referred toabove should be such that the integrity of the stored drug is maintainedby, for instance, preventing any ingress of moisture and/orcontaminating air into the storage chamber.

The frusto-conical shape also makes it possible to form the meteringmember in such manner that it occupies relatively little space, so thatthe inhalation passage can be shorter than in many prior inhalers,reducing the amount of suction required from the patient.

Preferably, the longitudinal axis of the frusto-conical wall lies, whenthe inhaler is held in its normal in-use position, between vertical andan angle of 60° to the vertical. More preferably, this axis lies at anangle of about 45° to the vertical.

The body of the inhaler preferably comprises a seat having an annularcontact surface making sliding contact with the metering surface, thecontact surface being frusto-conical in shape so as to define a socketwithin which the metering member is journalled for rotation between itsfirst and second positions. The inhaler then preferably comprises meansoperable to resiliently bias the metering member into contact with theseat.

Preferably, an inhaler in accordance with the present invention includesa chamber for containing moisture-absorbent material, with which chamberthe or each dispensing cup is moveable into register after a dose of thesubstance has been presented to the inhalation passage and before thatcup is again presented to the storage chamber. In this way, the emptycup can be dried prior to filling to reduce adhesion of the surface inthe cup. The filled dispensing cup may also move into register with thesame or another chamber for moisture-absorbent material as it travelsfrom the storage chamber to the inhalation passage. This could assist inpreventing migration of moisture from the inhalation passage into thestorage chamber.

The inhaler preferably includes display means which is indexed inassociation with the metering member to display an item of informationto the user. The display means may comprise counter means for countingthe number of times which a dispensing cup has been presented to theinhalation passage, and/or the number of doses remaining to be sopresented.

As has been mentioned above, the provision of a frusto-conical shapedmetering member is particularly advantageous in allowing greatermanufacturing tolerances than would be possible with otherconfigurations. If the metering member has a flat metering surface, asis the case in the above-described embodiment of U.S. Pat. No.2,587,215, then it is necessary to provide a separate axle or spigotjournalled on a part of the device. Such a separate axle is susceptibleto jamming by the ingress of powder between the contacting surfacesassociated with the axle.

Having regard to this, another aspect of the present invention providesan inhaler for delivering a substance in a finely divided form,comprising a body defining a storage chamber for the substance to bedelivered and further defining an inhalation passage through which airis inhaled in use; and a metering member operable to transfer avolumetric dose of the substance from the storage chamber to theinhalation passage, the metering member having a metering surface whichis indented to provide at least one dispensing cup and being moveablebetween a first position in which a dispensing cup is presented to thestorage chamber to receive a dose of the substance and a second positionin which a dose of the substance is presented to the inhalation passagein a dispensing cup which is upwardly open in use, the body comprising aseat having an annular contact surface making sliding contact with themetering surface, the contact surface being frusto-conical in shape soas to define a socket within which the metering member is journalled forrotation between its first and second positions.

Preferably, biassing means are provided to resiliently bias the meteringmember into contact with the seat.

In such an inhaler, the metering member preferably comprises afrusto-conical wall containing the dispensing cup or cups, thelongitudinal axis of the frusto-conical wall lying, when the inhaler isheld in its normal in-use position, between vertical and an angle of 60°to the vertical.

This inhaler may additionally comprise cup clearing means for ensuringthat the or each dispensing cup is substantially free from the substancebefore being presented to the storage chamber. The cup clearing meansmay comprise means for moving the or each dispensing cup into a positionfrom which, in normal use of the inhaler, any of the substance remainingin the dispensing cup would tend to fall, under the influence ofgravity, out of the cup, after a dose of the substance has beenpresented in the cud to the inhalation passage and before that cup isagain presented to the storage chamber. Alternatively or additionally,the cup clearing means may comprise an inhalation passage so formed thatthe dose of the substance presented to the inhalation passage issubjected to substantially the entire airflow through the inhalationpassage when air is drawn into the inhaler in use, or resilient wipingmeans for dislodging any residual substance from the or each cup after adose of the substance has been presented therein to the inhalationpassage and before that cup is again presented to the storagecompartment.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is exemplified in the accompanying drawings, in which:

FIG. 1 is a general perspective view of an inhaler of the invention;

FIG. 2 is a side view of the inhaler in use;

FIG. 3 is a longitudinal section through the inhaler;

FIG. 4 is section IV--IV of FIG. 3;

FIGS. 5 and 6 are exploded perspective views of the inhaler viewed fromopposite ends;

FIGS. 7a and 7b are exploded perspective views of the counter mechanismof the inhaler, again viewed from opposite ends; and

FIGS. 8a and 8b show the assembled counter mechanism viewed fromopposite ends.

DETAILED DESCRIPTION OF THE DRAWINGS

As shown in the external views of FIGS. 1 and 2, the inhaler comprises ahousing 1 which is provided with an air intake 2. A tubular mouthpiece 3projects from the housing.

Referring to FIGS. 3 to 6, the housing contains an internal body 4which, on its side remote from the mouthpiece 3, contains a recess 5that provides a seat for a metering member 6 which is rotatable aboutits axis in the recess. The metering member includes a portion having afrusto-conical metering surface 7 which includes a series ofcircumferentially arranged cup-like motoring depressions 8. The recess 5provides a seat of corresponding frusto-conical shape, the angulartolerance and circumferential form of the metering surface and of theseat being carefully monitored in manufacture to ensure a close slidingcontact between the two mating faces.

The opposite side of the body 4 includes a storage chamber 10 for a drugin the form of a micronised powder, the chamber 10 being arranged toregister with one of the depressions 8. A second, outer chamber 11surrounds the storage chamber 10 for containing a moisture absorbingmaterial such as silica gel granules. The second chamber 11 is open tothe depressions 8 on both sides of the depression which is currently inregister with the storage chamber 10, but the silica gel is preventedfrom migrating into the depressions by a shaped filter membrane 12. Thesame side of the body 4 further contains an inhalation passage 15 and awaste chamber 16, both of which register with one of the depressions 8.The inhalation passage 15 has a smooth internal contour and registerswith both the air inlet 2 and the mouthpiece 3. The air inlet 2 containsa filter membrane 17 for removing any contaminating particles that maybe drawn into the inlet. The waste chamber 16 contains a brush, a pieceof sponge rubber or other flexible wiping element 18 which projects intothe corresponding depression 8 to make wiping contact with the walls ofthe depression.

Referring more particularly to the inhalation passage 15, it can be seenfrom FIG. 3 that, when the inhaler is in use, the inhalation passage 15extends in a downwards direction from the air intake 2, at least to theposition where the dispensing cup 8 is presented to the inhalationpassage. The width of the inhalation passage 15 is relatively large atthe air intake, relatively small in the region of the dispensing cup andrelatively large again at the mouthpiece 3. The inhalation passageincludes a first relatively more-inclined portion extending generallydownwardly from the air intake 2 to the dispensing cup 8 and a secondrelatively less-inclined portion extending from the dispensing cup 8 tothe mouthpiece 3. Dispensing cup 8 is situated on the outside of thebend linking these two portions of the inhalation passage. Opposite thedispensing cup, the wall of the inhalation passage bulges across theinhalation passage towards a dispensing cup to create a restrictedpassageway in the region of the dispensing cup. In this region, theshape of the inhalation passage results in the air being bothaccelerated and directed towards the dispensing cup so that there is ahighly efficient pick-up of material from the cup.

The frusto-conical head of the metering member 6 is secured to aco-axial circular ratchet formation 20 followed by a drum 21. A springwasher 22 acts between an end face of the drum 21 and the housing 1 tourge the metering member 6 against its seat in the recess 5. An indexingbutton 25 projects from the housing 1 adjacent to the inlet 2 and issecured to an integral indexing finger 26 for engagement with theratchet formation 20. A spring finger 27, again integral with the button25, projects transversely of the indexing finger 26 to engage theinternal body 4 and thus urge the button to project from the housing 1.

A tape 30 is wound into a roll 31 which is freely rotatable on a pin 32projecting from the inside of the housing 1. The leading end of the tape30 is secured to the drum 21, onto which it is wound from the roll 30upon rotation of the metering member 6. The tape 30 is routed past awindow 33 in the housing 1 through which a contiguous series of numbersor other information carried on the tape is displayed.

In use, the inhaler will normally be supplied as a sealed unit with thestorage chamber 10 pre-filled with medicament or other substance in adry, finely divided form. With the button 25 uppermost, the depression 8which is in register with the storage chamber 10 will fill with a fixedvolume of the medicament. With the inhaler held in one hand themouthpiece 3 is inserted into the mouth as shown in FIG. 2 and thebutton 25 is depressed using the index finger so that the indexingelement 26 causes the metering member 6 to rotate by one position, thusbringing the next, empty depression 8 into register with the storagechamber 10. At the same time a filled depression comes into registerwith the inhalation passage 15. Thus, when air is drawn through theinhalation passage 15 via the mouthpiece 3, the internal contours of theinhalation passage causes the air to impinge on the material still heldin the depression 8, causing the powder to be mixed into the air flowand, after passing through the mouthpiece 3, enter the mouth and airpassages of the user.

It should be noted that the powder in the depression 8 is subjected tothe entire airflow through the inhalation passage 15, from the airintake 2 to the mouthpiece 3, which enables the user more readily toachieve a full dose, and also promotes substantially complete removal ofthe powder from the depression 8.

As the depressions travel around the axis of the metering member withsuccessive indexing movements of the button 25, they move past thewiping element 18 so that any residue of powder remaining in thedepression is dislodged therefrom to fall into the waste chamber 16.Further travel of the depression causes it to move in register with thedrying chamber 11 so that the silica gel can absorb any moisture fromthe depression before it comes into register with the storage chamber 10to be refilled with medicament. The filled depressions may also move inregister with the drying chamber 12 to reduce the possibility ofmoisture migrating from the inhalation passage 15 to the storage chamber10. This may additionally ensure that the medicament remains dry,thereby ensuring that the vase majority of the medicament can be easilyremoved from the depression into the inhaled airflow.

It is important that the movement of a dose of powder to the dispensingposition in the inhalation passage 15 is effected in such fashion as tomaintain good sealing of the powder in the storage chamber 10, so thatthe integrity of the powder is preserved. This is facilitated by theprovision of the frusto-conical shape of the metering surface 7 and ofthe seat for it provided by the recess 5; such a shape makes it possibleto achieve a good seal between the metering surface 7 and its seat withless demanding tolerances than are feasible when other shapes are used.Providing that the angular tolerance is maintained (which is relativelysimple), other manufacturing tolerances are accommodated by theself-sealing arrangements of the metering surface 7 and the seatprovided by the recess 5.

In normal use of the inhaler, repeated indexing of the motoring member 6will not deposit multiple doses of the substance into the inhalationpassage. Instead, each dose will simply be carried round in thedepression 8 until it is discarded into the waste chamber 16.

Each time the motoring member is indexed, new information is carriedinto the window 33 by the tape 30. This information could simply be anumber indicating how many doses have been used, or how many remain tobe used, or both. The window could also display other information suchas the time when the next dose should be taken.

Normally, the device will be disposed of once the intended number ofdoses has been used. It is, however, envisaged that the internal body 4could contain a replaceable cartridge containing a fresh supply ofmedicament and possibly also fresh silica gel, new filters 12 and/or 17,and a fresh tape 31. This tape could be partially wound onto areplaceable drum 21 which engages the frusto-conical metering head 6.

A modified counting arrangement is shown in FIGS. 7a, 7b, 8a and 8b. Thehousing 1 contains a circular internal recess 36 which receives an outerring 37 and an inner disc 38 which are arranged co-axially with themetering member 6. The disc 38 carries the units 0 to 9 at 36° intervalswhereas the ring 37 is marked in multiples of tens at regular angularintervals. The tens and units are disposed so that they can both bedisplayed through a window 39 in the housing 1. The disc 38 is connectedto, or driven by, the metering member 6 and carries an integral springarm 40 which carries a pin 41 to act as a cam follower. Whenever thedisc 38 completes one rotation, the arm 39 engages a cam 44 secured tothe interior of the housing 1, which causes the cam follower 41 toengage in one of a series of notches 45 around the outer periphery ofthe ring 37. This, in turn, indexes the ring by one angular position oneach rotation of the disc 38. The number displayed in the window 40 canthus be incremented from, say, 1 to 200 to count the number of dosesused. Instead of a ring surrounding the disc 38, a second transparentdisc could be disposed behind the disc 38 so that the units are visiblethrough the second disc, which again carries multiples of tens.

I claim:
 1. An inhaler for delivering a substance in a finely dividedform, comprising a body defining a storage chamber for the substance tobe delivered and further defining an inhalation passage through whichair is inhaled, and a metering member having a metering surface which isindented to provide at least one dispensing cup, and means for movingthe metering member between a first position in which a dispensing cupis presented to the storage chamber to receive a volumetric dose of thesubstance and a second position in which a volumetric dose of thesubstance is presented to the inhalation passage in an upwardly opendispensing cup and in which, in normal use of the inhaler, at least amajor proportion of the substance in the dispensing cup is retained inthe cup by the influence of gravity before air is drawn through theinhalation passage, the body comprising a seat having an annular contactsurface making sliding contact with the metering surface, the meteringsurface being seated against the contact surface and comprising afrusto-conical wall and the contact surface being correspondinglyfrusto-conical in shape so as to define a socket within which themetering member is journalled for rotation solely by contact between thefrusto-conical wall and the contact surface between its first and secondposition.
 2. An inhaler according to claim 1 in which the meteringmember is resiliently biased into contact with the seat.
 3. An inhaleraccording to claim 1 in which the longitudinal axis of thefrusto-conical wall which the metering surface comprises lies, when theinhaler is held in its normal in-use position, between vertical and anangle of 60° to the vertical.
 4. An inhaler according to claim 1,additionally comprising means for ensuring that the or each dispensingcup is substantially free from the substance before being presented tothe storage chamber.
 5. An inhaler according to claim 4, in which theinhalation passage is so formed that the dose of the substance presentedto the inhalation passage is subjected to substantially the entireairflow through the inhalation passage when air is drawn into theinhaler in use.
 6. An inhaler according to claim 1 in which, in thenormal use of the inhaler, substantially all of the substance in thedispensing cup when in its second position will remain in the cup.
 7. Aninhaler for delivering a substance in a finely divided form, comprisinga body defining a storage chamber for the substance to be delivered andfurther defining an inhalation passage through which air is inhaled, anda metering member having a metering surface which is indented to provideat least one dispensing cup, and means for moving the metering memberbetween a first position in which a dispensing cup is presented to thestorage chamber to receive a volumetric dose of the substance and asecond position in which a volumetric dose of the substance is presentedto the inhalation passage in an upwardly open dispensing cup and inwhich, in normal use of the inhaler, at least a major proportion of thesubstance in the dispensing cup is retained in the cup by the influenceof gravity before air is drawn through the inhalation passage, the bodycomprising a seat having an annular contact surface making slidingcontact with the metering surface, the metering surface comprising afrusto-conical wall and the contact surface being correspondinglyfrusto-conical in shape so as to define a socket within which themetering member is journalled for rotation between its first and secondposition, means for ensuring that the or each dispensing cup issubstantially free from the substance before being presented to thestorage chamber, means for moving the or each dispensing cup into aposition from which, in normal use of the inhaler, any of the substancesremaining in the dispensing cup would tend to fall, under the influenceof gravity, out of the cup, after a dose of the substance has beenpresented therein to the inhalation passage and before that cup is againpresented to the storage chamber to ensure that the or each dispensingcup is substantially free from the substance before being presented tothe storage chamber.
 8. An inhaler for delivering a substance in afinely divided form, comprising a body defining a storage chamber forthe substance to be delivered and further defining an inhalation passagethrough which air is inhaled, and a metering member having a meteringsurface which is indented to provide at least one dispensing cup, andmeans for moving the metering member between a first position in which adispensing cup is presented to the storage chamber to receive avolumetric dose of the substance and a second position in which avolumetric dose of the substance is presented to the inhalation passagein an upwardly open dispensing cup and in which, in normal use of theinhaler, at least a major proportion of the substance in the dispensingcup is retained in the cup by the influence of gravity before air isdrawn through the inhalation passage, the body comprising a seat havingan annular contact surface making sliding contact with the meteringsurface, the metering surface comprising a frusto-conical wall and thecontact surface being correspondingly frusto-conical in shape so as todefine a socket within which the metering member is journalled forrotation between its first and second position, means for ensuring thatthe or each dispensing cup is substantially free from the substancebefore being presented to the storage chamber, resilient wiping meanspermanently mounted within the body of the inhaler for dislodging anyresidual substance from the or each cup after a dose of the substancehas been presented therein to the inhalation passage and before that cupis again presented to the storage chamber.